AN INTEGRATED DATA ACQUISITION AND ANALYSIS APPROACH DECREASES SATURATION UNCERTAINTY AND PROVIDES VALUABLE SECONDARY INFORMATION IN DIFFICULT CONDITIONS

摘要

A review of available saturation information to support an infill well target concluded that sufficient uncertainty existed to warrant further well interventions to acquire data supporting the proposed location. Mixed water salinity within the formation added to the complexity of surveillance. Under these conditions traditional sigma analysis can be easily confused while the logged intervals are long enough to effectively preclude the exclusive use of CO logging techniques. The data acquisition plan for the well intervention used a combination of limited CO logging and Sigma logging as well as a trial of a new pulse neutron saturation determination technique (FluidView). The sigma data recorded covered the entire reservoir interval allowing comparison against previously acquired time lapse data while the CO logging was targeted at a much shorter reservoir section of high importance. The new FluidView technique is seen to be complementary to the sigma analysis with data being acquired contemporaneously over the entire reservoir and has significantly less salinity dependence than traditional sigma but has a data acquisition speed which is half that of sigma and 20 times faster than CO. Analysis of the combined data sets provided valuable insights into saturation, vertical profile of the water sweep, current fluid movements and has led to a better understanding of residual oil saturation and distribution behind the flood front.